package io.summer.demo.config;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import java.io.IOException;

/**
 * @author ml
 */
public class CustomObjectMapperConfig {
  @Bean
  @Primary
  @ConditionalOnMissingBean(ObjectMapper.class)
  public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
    ObjectMapper objectMapper = builder.createXmlMapper(false).build();

    // 通过该方法对mapper对象进行设置，所有序列化的对象都将按改规则进行系列化
    // Include.Include.ALWAYS 默认
    // Include.NON_DEFAULT 属性为默认值不序列化
    // Include.NON_EMPTY 属性为 空（""） 或者为 NULL 都不序列化，则返回的json是没有这个字段的。这样对移动端会更省流量
    // Include.NON_NULL 属性为NULL 不序列化
    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
    objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    // 字段保留，将null值转为""
    objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
      @Override
      public void serialize(Object o, JsonGenerator jsonGenerator,
                            SerializerProvider serializerProvider)
        throws IOException {
        jsonGenerator.writeString("");
      }
    });
    return objectMapper;
  }
}
